Airport extreme changes the name of my computer

My airport extreme keeps changing the name of my computer on the network. If the name is, let's say MyComputer, every once in a while I get a message that this name is used by some other computer and then changes it to MyComputer (2). It's now on MyComputer (8). My other computers connected to the network all have different names. Any idea what is causing this and how to stop it from happening?

Thanks